Scientists in Japan claim to have developed a rudimentary human liver and a precursor of a human eyeball in the lab using stem cells, a feat they say could be a boon for the future organ replacement.

At Yokohama City University in Japan, a team led by Takanori Takebe grew a small, rudimentary liver using a recipe of just three types of cells.

First, the team placed genetically reprogrammed human skin cells, called “induced pluripotent stem cells,” on growth plates in a specially designed chemical bath. After nine days, the cells began developing into hepatocytes, or liver cells.

Two days later, the cell assortment had self-organised to form a 3D “liver bud” – a 5mm-wide chunk of tissue that performed basic liver functions.

When they grafted the liver bud into a mouse, the team said the tiny organ’s blood vessels worked correctly and it successfully metabolised some drugs that human livers metabolise but which mouse can’t.

Meanwhile, Yoshiki Sasai and colleagues at the RIKEN Center for Developmental Biology, reported that they had managed to induce human stem cells called “retinal precursor cells” to develop into a central component of the human eye called an optic cup.

In a petri dish, the cells spontaneously bulged to form a bubble called an eye vesicle, which folded back on itself to create a half-millimeter-wide pouch layered with retinal cells – the optic cup.